The following relates generally to wireless communication, and more specifically to hybrid automatic repeat request (HARQ) feedback in unlicensed radio frequency (RF) spectrum.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system). A wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
In some wireless communications systems, devices may communicate using resources of a shared or unlicensed RF spectrum band. Such communication may be contention-based, and the shared nature of the wireless medium may introduce complexities for transmitting or receiving certain types of information, including control information. Systems that operate without accounting or compensating for the opportunistic nature of shared-spectrum communication may be inefficient or error-prone.